The drug and homeless problem can be solved with a wall. These sites need to be isolated from society. Get the homeless (drug users) to agree by giving them food, shelter, and the drug of choice. Get the left to agree by putting a voting booth in the homeless shelter at election time. And get the rest of us to agree by fencing the site off and not permitting them to panhandle or sleep on the street.
BTW, a wall also solves the border and the school safety issues. When will we see it?
Which neighborhood? Lefties will always volunteer for the common good.